The present invention relates to a vehicle security device and vehicle security system for deterring unauthorized use of a vehicle by a third party and theft of a vehicle.
Japanese Laid-Open Patent Publication No. 2004-108196 describes an example of a vehicle security apparatus that improves the security of a vehicle. The vehicle security apparatus includes a portable device, which is held by an owner (user) of the vehicle, and an in-vehicle device, which is installed in the vehicle. The portable device and the in-vehicle device communicate with each other. More specifically, the in-vehicle device periodically transmits a wireless signal (request signal) to the passenger compartment. When receiving the request signal, the portable device returns a wireless signal (ID code signal) to the in-vehicle device. The ID code signal includes a predetermined ID code. The in-vehicle device then compares the ID code included in the ID code signal with an ID code preset for the in-vehicle device. When the ID codes match, the in-vehicle device enables the engine to be started.
The vehicle security device includes an emergency key to enable starting of the engine when battery drainage occurs in the portable device. The emergency key is formed by a mechanical key, which is insertable into a key cylinder located in the passenger compartment, and a transponder, which is incorporated in the mechanical key and activated by electromagnetic force to transmit a wireless signal (transponder signal) including a unique transponder code.
In a normal state, rotation of the key cylinder is disabled. The key cylinder includes an antenna from which electromagnetic energy is generated. When the mechanical key is inserted in the key cylinder, the key cylinder generates electromagnetic energy in a small area proximal to the key cylinder. The electromagnetic energy activates the transponder and transmits the transponder signal. Upon receipt of the transponder signal, the in-vehicle device compares the transponder code included in the transponder signal with a transponder code preset for the in-vehicle device. When the transponder codes match, the in-vehicle device enables the key cylinder to be rotated. This prevents the engine from being started even if the mechanical key is duplicated or if a foreign object is inserted into the key cylinder. As a result, the security of the vehicle is improved.
Although such a conventional vehicle security apparatus improves the security of a vehicle, theft of the portable device cannot be prevented. Accordingly, it is desirable that the security function of the vehicle security apparatus be improved.